Modeling for coupled thermal and humidity environments in spaces with impinging jet ventilation using zonal model theory

Thermal stratification, due to the coupling of heat and moisture transfer, also results in humidity stratification. While many models address thermal stratification in impinging jet ventilation (IJV) systems, few consider its humidity distribution. This study develops a zonal model that simultaneously predicts vertical temperature and humidity profiles for IJV. The space is vertically divided into sub-zones, with mass and energy balance equations established for each. A critical parameter in the model is the inter-zonal mass flow rate (m), which governs the exchange of air between adjacent zones and thus determines the transport of heat and moisture. To quantify this parameter, CFD simulations are performed under various operating conditions, and a height-dependent function is derived for m. The model’s accuracy is validated by comparing the predicted temperature and humidity distributions with numerical results. The results show that the proposed model achieves a mean relative error of 6.95 % for temperature prediction and of 1.41 % for humidity prediction. Besides, the proposed model is compared with original zonal model considering only heat transfer. It reveals that the maximum temperature prediction discrepancy for the original model reaches up to 5.03 °C, whereas the proposed zonal model shows a discrepancy of only 1.99 °C. This underscores the importance of considering the coupling of air temperature and moisture in indoor environmental studies. The current model not only provides a more accurate description of temperature distributions for IJV but also enables the prediction of indoor humidity distribution—a capability that the original zonal model lacks.